AWS SQS Terminologies

SQS - is FIFO queue , First in First Out.

Introduction:

Topic vs Queue:

Queue : one to one connection. Topic: one to many connection.

Terminologies :

Message retention period:

Unconsumed messages will be deleted after this retention period.

Visibility Timeout:

TimePeriod given to he consumer to process the message. During visibility timeout period, the messages wont be available to other consumer threads to receive. After the " visibility timeout " period, if the consumer which was trying to process the message didn’t process or delete the message from the queue, then the message will be again visible in the queue to receive.

Dead Letter queue:

unprocessed message will go to dead letter queue if DLQ is enabled.

Purge:

If you want to delete all the messages in the queue ,but if you don’t want to delete the SQS queue , you can use purge.

Inflight messages:

Messages received from the Producer and it is not yet received by the consumer

Producer - Send messages to the queue. Consumer - Who receives messages from the queue.

Delivery delay:

When the producer posted the message to the queue and after message added to the queue, if you have delivery delay value set, then the message will be hidden for the consumers for that delay period.